Method and apparatus of configuring timing of uplink transmission

ABSTRACT

The present disclosure is to provide a method of configuring timing of uplink (UL) transmission, comprising, receiving, by a user equipment (UE), configuration information on carrier aggregation (CA) of at least one frequency division duplex (FDD) cell and at least one time division duplex (TDD) cell; and adjusting, by the UE, starting timing of a UL subframe in a cell participating in the CA.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/511,219,filed Jul. 15, 2019, which is a continuation of application Ser. No.16/025,894, filed Jul. 2, 2018, now U.S. Pat. No. 10,397,945, which is acontinuation of application Ser. No. 14/909,049, which is the NationalStage of PCT/KR2014/006999, filed Jul. 30, 2014, now U.S. Pat. No.10,057,919, which claims priority to Chinese Patent Application No.201310325414.7, filed Jul. 30, 2013 and Chinese Patent Application No.201410050500.6, filed Feb. 13, 2014, each of which are incorporated byreference into the present disclosure as if fully set forth herein.

BACKGROUND 1. Field

The present disclosure relates to wireless communications systems, andparticularly, to a method and an apparatus of configuring timing foruplink transmission in a system where carrier aggregation (CA) isapplied to both frequency division duplex (FDD) cells and time divisionduplex (TDD) cells.

2. Description of Related Art

3GPP LTE (Long-Term Evolution) systems support both FDD and TDD.

FIG. 1 is a schematic diagram illustrating a frame structure of an FDDsystem.

As shown in FIG. 1, in an FDD system, each radio frame (101) has alength of 10 ms, and includes 10 subframes. Each subframe (103) has alength of 1 ms, and contains two time slots (105) each of which lasts0.5 ms, i.e., the k'th subframe contains time slot 2k and time slot2k+1, k=0,1, . . . ,9.

FIG. 2 is a schematic diagram illustrating a frame structure of a TDDsystem.

As shown in FIG. 2, in a TDD system, each radio frame (201) of 10 ms isdivided into two equal half-frames each of which lasts 5 ms. Eachhalf-frame (203) includes 8 time slots each of which lasts 0.5 ms, and 3special fields, i.e. Downlink Pilot Time Slot (DwPTS) (211), GuardingPeriod (GP) (213) and Uplink Pilot Time Slot (UpPTS) (215). The 3special fields altogether last 1 ms. Each subframe (205) is composed oftwo consecutive time slots (207), i.e., the k'th subframe includes timeslot 2k and time slot 2k+1. A downlink transmission time interval (TTI)is defined in a subframe.

A TDD system supports 7 types of uplink/downlink (UL/DL) configurations,as shown in Table 1. In the table, D denotes a downlink subframe, Udenotes an uplink subframe, S denotes a special subframe including the 3special fields.

TABLE 1 LTE TDD UL/DL configuration Switch- Configuration pointSub-frame ID serial number periodicity 0 1 2 3 4 5 6 7 8 9 0  5 ms D S UU U D S U U U 1  5 ms D S U U D D S U U D 2  5 ms D S U D D D S U D D 310 ms D S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D DD D D D D 6  5 ms D S U U U D S U U D

The frame structures shown in FIG. 1 and FIG. 2 are ideal framestructures of LTE systems. In practice, a base station and a UE may havedifferent timing for sending and receiving subframes due to propagationdelay. In an FDD system, timing of UL/DL subframes of a base station aregenerally aligned. In a TDD system, a time interval is generally addedbetween a UL subframe and a DL subframe to allow the base station totransit from a receiving state to a sending state. According to LTE TDDstandards, the time interval is 20 us, i.e., timing for receiving a ULsubframe by a base station is 20 us prior to ideal subframe timing.

FIG. 3 illustrates a method of determining starting timing of sending aUL subframe by a UE.

The UE takes timing of a DL signal received from the base station as areference for determining UL starting timing. Due to propagation delay,the UE needs to advance the transmission of the UL signal by a certaintime period to guarantee the UL signal of the UE satisfies a requiredtiming relation when received by the base station. The time advance (TA)(301) of the UE is (N_(TA)+N_(TA offset))×T_(S) seconds T_(S) is asampling interval obtained by using a sampling frequency of 30.72 MHz.In an FDD system, N_(TA offset) equals 0, and the base station adjuststransmission TA of a UE by adjusting the value of N_(TA) to makeboundaries of UL subframes and DL subframes aligned at the base station.In a TDD system, N_(TA offset) equals the value of 624, N_(TA) isconfigured by the base station. The TA actually used by the UE is(N_(TA)+N_(TA offset))×T_(S) seconds, so that the timing of receivingthe UL subframe at the base station is 20 us prior to the ideal timingof TDD subframes, which provides time for the base station to transitfrom receiving to sending.

In an LTE system, a UE triggers a random access process by sending arandom access preamble signal when attempting to access the system. TheUE determines starting timing of preambles of physical random accesschannel (PRACH) preamble formats 0-3 by taking N_(TA)=0. As such, for anFDD system, the starting timing of a PRACH preamble signal is directlyobtained by using the timing for receiving DL signals from the basestation; for a TDD system, the starting timing of a PRACH preamblesignal is 20 us prior to timing for receiving DL signals from the basestation. With respect to PRACH preamble signal format 4, the UEdetermines timing of the end position of the UpPTS time slot by takingN_(TA)=0, i.e., sending the preamble signal 4832 T_(S) and 20 us priorto the timing of receiving DL signals from the base station.

In an LTE-A (LTE-advanced) system, multiple CC (component carriers) areaggregated to obtain larger working bandwidth, i.e., CA (carrieraggregation). The aggregated carriers constitute downlink and uplinklinks in the communication system, therefore larger transmission ratescan be achieved. A base station may configure a UE to work in multipleCells which include a Pcell (Primary Cell) and multiple Scells(Secondary Cell). According to LTE Release 11, it is configured thatHARQ-ACK of all Cells that are configured to be received by the UE isfed back in a UL subframe in a Pcell.

According to LTE Release 11 specification, multiple Cells can onlycollaborate with each other through CA when they are working under thesame duplexing mode. In order to further improve system performances,future studies focus on CA systems that support both aggregated FDD andaggregated TDD. But as illustrated above, FDD systems and TDD systemshandle timing of uplink subframes differently, i.e., TDD systems uses anextra TA of 20 us compared to FDD systems. There is urgent need forfinding a way to coordinate timing of uplink transmission of FDD Cellsand TDD cells within a CA system.

SUMMARY

The present disclosure is to provide a method of configuring timing ofuplink (UL) transmission, comprising, receiving, by a user equipment(UE), configuration information on carrier aggregation (CA) of at leastone frequency division duplex (FDD) cell and at least one time divisionduplex (TDD) cell; and adjusting, by the UE, starting timing of a ULsubframe in a cell participating in the CA. The present disclosure is toprovide an apparatus, comprising: a configuring module and an adjustingmodule, wherein the configuring module is configured to receiveconfiguration information, and performing carrier aggregation (CA) offrequency division duplex (FDD) cells and time division duplex (TDD)cells according to the configuration information; and the adjustingmodule is configured to adjust starting timing of a UL subframe in acell participating in the CA.

The present disclosure is to provide a method enables UL subframes ofmultiple cells to have the same or similar starting timing in a CAsystem where CA is applied to both FDD cells and TDD cells. In anexample, starting timing of UL subframes in an FDD cells may be adjustedto be consistent with or similar to that of a TDD cell. Thus, overlap oftwo successive subframes resulted from non-aligned timing can bereduced, system performances can be improved, and the CA system'scapability of anti-timing-offset can also be enhanced. The performanceimprovements are only reflected in those UEs that support CA of both FDDcells and TDD cells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a frame structure of an FDDsystem;

FIG. 2 is a schematic diagram illustrating a frame structure of a TDDsystem;

FIG. 3 is a schematic diagram illustrating TA;

FIG. 4 is a flowchart illustrating a method of configuring timing of ULtransmission in accordance with an example of the present disclosure;and

FIG. 5 is a schematic diagram illustrating modules of an apparatus inaccordance with an example of the present disclosure.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skilled in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of thedisclosure. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of thedisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent disclosure is provided for illustration purpose only and not forthe purpose of limiting the disclosure as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

In an LTE system working in only one duplexing mode, the manner ofhandling starting timing of an UL subframe is related with the duplexingmode according to LTE standards.

In an FDD cell, starting timing of a UL subframe sent by a UE is(N_(TA)+N_(TA offset))×T_(S) seconds prior to starting timing of a DLsubframe corresponding to the UL subframe received by the UE, andN_(TA offset)=0.

In a TDD cell, starting timing of an UL subframe sent by a UE is(N_(TA)+N_(TA offset))×T_(S) seconds prior to starting timing of a DLsubframe corresponding to the UL subframe received by the UE, andN_(TA offset)=624 N_(TA) denotes the TA configured by a base station forthe UE.

During initial random access, a UE determines starting timing forsending a PRACH preamble signal by using N_(TA)=0. As such, the startingtiming of UL subframes of the TDD system has an extra time advance (TA)of 20 us compared to that of the FDD system to enable the base stationto transit between sending and receiving.

In a CA system where CA is applied to both FDD cells and TDD cells, ifthe manner defined in LTE Release 11 is re-used in each carrier, a UEmay have a 20 us offset between the starting timing of an FDD cell and aTDD cell, thus starting timing of UL subframes are not aligned. Thenon-aligned timing results in overlap of two successive subframes in theCA system. But LTE Release 11 standards provide no mechanism foroptimizing system performances when the overlap occurs. Generally,system performances can be improved by aligning starting timing of ULsubframes in UL carriers of a UE. In a CA system, if starting timing ofUL subframes of a UE in multiple cells are not aligned, LTE Release 11standards support a maximum timing offset of 31.3 us amongst multiplecells for UL transmission. Since the maximum tolerable timing offset isonly slightly larger than 20 us, the timing offset of 20 us can greatlyimpair the capabilities of anti-timing-offset of the system.

Based on the above analysis, the timing offset of UL subframes betweenFDD cells and TDD cells resulted in different duplexing modes adverselyaffect performances of a CA system where CA is applied to both FDD cellsand TDD cells. To address the above issues, examples of the presentdisclosure provide a method of configuring timing of UL transmission ina system where CA is applied to both FDD cells and TDD cells.

FIG. 4 is a flowchart illustrating a method of configuring timing of ULtransmission in accordance with an example of the present disclosure.

The method of the present disclosure may include the followingprocedures.

At block 401, a UE receives configuration information on carrieraggregation (CA) of at least one FDD cell and at least one TDD cell.

The configuration information may only specify that the system supportsCA of both FDD cells and TDD cells. In another example, theconfiguration information may also include control information which isused for adjusting starting timing of UL subframes in cells. Forexample, the control information may be a parameter indicating a timingoffset N_(TA) ^(offset) The control information for starting timing ofUL subframes may be sent in FDD cells only, or may be sent in both FDDcells and TDD cells.

At block 402, the UE adjusts starting timing of a UL subframe in a cellparticipating in the CA.

The starting timing of uplink subframes in one or multiple cells thatparticipate in CA may be different from starting timing defined in LTERelease 11 for uplink subframes under the same duplexing mode.

An example of the manner of handling TA may include: adding a TA ofN_(TA offset)×T_(S) to starting timing defined in LTE Release 11 for ULsubframes in FDD cells.

Given that the N_(TA)×T_(S) seconds refers to the TA configured for a UEwhen the cell conforms to LTE Release 11, the TA of a UE is(N_(TA)+N_(TA offset))×T_(S) seconds in a CA system where CA is appliedto both FDD cells and TDD cells. In an example, the TA configured by abase station for the UE may have already included the extraN_(TA offset)×T_(S) seconds, i.e., the base station may configure the TAof the UE to be (N_(TA)+N_(TA offset))×T_(S) seconds. In anotherexample, the base station may conform to LTE Release 11 and configurethe TA of the UE to be N_(TA)×T_(S) seconds, and the UE addsN_(TA offset)×T_(S) seconds to the TA when performing UL transmission,i.e., the actual TA is (N_(TA)+N_(TA offset))×T_(S) seconds.

In the above examples, the N_(TA offset) may be a pre-defined value.Alternatively, the N_(TA offset) may also be a value decided by the basestation or a value decided using other mechanisms that do not involveexchange of higher-layer signaling when the base station configures a TAwhich has already included the N_(TA offset)×T_(S) seconds. The value ofN_(TA offset) asset can keep the maximum timing offset of ULtransmissions between TDD cells and FDD cells consistent with that inLTE Release 11 CA systems. In an example, when N_(TA offset)=624N_(TA offset)×T_(S)=20 us, which enables starting timing of UL subframesin FDD cells to be consistent with that in TDD cells.

Another example of the manner of handling TA may include: makingstarting timing of a UL subframe of a UE (N_(TA)+N_(TA) ^(offset))×T_(S)seconds prior to starting timing of a DL subframe received by the UE inthe cell based on control information for starting timing of ULsubframes in the cell sent by the base station, e.g., a timing offsetparameter N_(TA) ^(offset). In the example, N_(TA)×T_(S) denotes the TAconfigured for the UE when the cell conforms to LTE Release 11. In anexample, the TA configured by a base station for the UE may have alreadyincluded the extra N_(TA) ^(offset)×T_(S) seconds, i.e., the basestation may configure the TA of the UE to be (N_(TA)+N_(TA)^(offset))×T_(S) seconds. In another example, the base station mayconform to LTE Release 11 and configure the TA of the UE to beN_(TA)×T_(S) seconds, and the UE adds N_(TA) ^(offset)×T_(S) seconds tothe TA during UL transmission, i.e., the actual TA is (N_(TA)+N_(TA)^(offset))×T_(S) seconds.

The N_(TA) ^(offset) may be sent to all of UEs via broadcast signaling.Alternatively, the N_(TA) ^(offset) may be configured individually foreach UE through radio resource control (RRC) signaling. The method maybe applied to FDD cells only, i.e., adding N_(TA) ^(offset)×T_(S)seconds to the starting timing of UL subframes specified in LTE Release11 to adjust starting timing of UL subframes in FDD cells.Alternatively, the method may be applied to both FDD cells and TDDcells, i.e., using N_(TA) ^(offset) instead of N_(TA offset)=624 togenerate an extra TA of N_(TA) ^(offset)×T_(S) i TDD cells. The value ofN_(TA) ^(offset) can keep the maximum timing offset of UL transmissionsbetween TDD cells and FDD cells consistent with that in LTE Release 11CA systems. In an example, when N_(TA) ^(offset)=624, N_(TA)^(offset)×T_(S)=20 us, which enables starting timing of UL subframes inFDD cells to be consistent with that in TDD cells.

The method as shown in FIG. 4 enables UL subframes of multiple cells tohave the same or similar starting timing in a CA system where CA isapplied to both FDD cells and TDD cells. In an example, starting timingof UL subframes in an FDD cells may be adjusted to be consistent with orsimilar to that of a TDD cell. Thus, overlap of two successive subframesresulted from non-aligned timing can be reduced, system performances canbe improved, and the CA system's capability of anti-timing-offset canalso be enhanced. The performance improvements are only reflected inthose UEs that support CA of both FDD cells and TDD cells.

The following are a few examples of adjusting starting timing of ULsubframes in cells.

EXAMPLE ONE

According to the above analysis, timing of a base station receiving ULsubframes in a cell may be adjusted in a CA system where CA is appliedto both FDD cells and TDD cells to make starting timing of UL subframesof a UE in FDD cells and TDD cells become consistent with or close toeach other. Suppose a UE works only in one of the cells. Since timing ofUL subframes in a cell has been adjusted on the basis of the timingspecified in LTE Release 11 for the same duplexing mode, starting timingof UL subframes of a UE needs to be adjusted accordingly to improvesystem performance.

Taking the random access process in an FDD system as an example, if a UEstill follows the random access process as defined in LTE Release 11,performances of the random access may be dissatisfactory. Suppose PRACHformat 0 is configured, the CP length is 3168·T_(S)an effective preamblesequence has a length of 24576·T_(S), and the guarding period followingthe random access preamble is 2976·T_(S), i.e., approximately 97 us. ThePRACH format 0 can support a maximum cell coverage radius of 14.5 km. Ina CA system where CA is applied to both FDD cells and TDD cells, supposethe timing of receiving UL subframes in an FDD cell has been advanced by20 us to be consistent with the timing of UL subframes in a TDD cell. Ifa UE determines starting timing of a PRACH preamble in the FDD cellstill using the manner defined for an LTE single carrier system, thissituation equivalent to that the guarding period following the randomaccess preamble is reduced by 20 us, i.e., the maximum cell coverageradius of the PRACH format 0 is reduced by 3 km, i.e., 11.5 km.

In the CA system where CA is applied to both FDD cells and TDD cells,when a UE works in only one cell, the cell may be an FDD cell or a TDDcell. In an example, a solution may include making starting timing of anUL subframe to be sent by the UE (N_(TA)+N_(TA offset))×T_(S) secondsprior to the starting timing of a DL subframe received by the UE fromthe cell at block 402.

The N_(TA)×T_(S) sdenotes the TA configured for the UE when the cellconforms to LTE Release 11. The N_(TA offset)×T_(S) denotes anadditional TA to be added to the cell obtained by using the first mannerof handling TA in block 402, e.g., N_(TA offset)=624. The N_(TA)×T_(S)denotes the TA configured for the UE when the cell conforms to LTERelease 11. In an example, the base station may configure a TA for theUE which has already included the extra N_(TA offset)×T_(S) seconds,i.e., the base station may configure the TA of the UE to be(N_(TA)+N_(TA offset))×T_(S) seconds. In another example, the basestation conforms to LTE Release 11 and configures the TA of the UE to beN_(TA)×T_(S) seconds, and the UE adds N_(TA offset)×T_(S) seconds to theTA during UL transmission, i.e., the actual TA is(N_(TA)+N_(TA offset))×T_(S) seconds. In an example, the UE may useN_(TA)=0 during an initial random access process, i.e., for themechanism where it is pre-defined that N_(TA offset)=624, the startingtiming for sending the PRACH pre-amble signal may be determined to beN_(TA offset)×T_(S)=20 us prior to the starting timing of a DL subframereceived by the UE from the cell. As such, the cell coverage of thePRACH pre-amble signal can be maintained unchanged.

In the CA system where CA is applied to both FDD cells and TDD cells, Ivanother method may include configuring a timing offset parameter N_(TA)^(offset) for the cell at block 401. N_(TA) ^(offset)×T_(S) denotes theTA to be added to the cell obtained by using the second manner ofhandling TA in block 402. The N_(TA) ^(offset) may be sent via broadcastsignaling, or may be sent to each UE via RRC signaling. In an example,the base station may configured a TA for the UE which has alreadyincluded the extra N_(TA) ^(offset)×T_(S) seconds, i.e., the basestation may configure the TA of the UE to be (N_(TA)+N_(TA)^(offset))×T_(S) seconds. In another example, the base station conformsto LTE Release 11 and configures the TA of the UE to be N_(TA)×T_(S)seconds, and the UE adds N_(TA) ^(offset)×T_(S) seconds to the TA duringUL transmission, i.e., the actual TA is (N_(TA)+N_(TA) ^(offset))×T_(S)seconds. The N_(TA) ^(offset) may be configured for FDD cells only, orbe configured for all of cells regardless of duplexing modes.

When a UE works only in a cell that has configured with N_(TA)^(offset), if the N_(TA) ^(offset) is configured for the cell viabroadcast signaling in block 402, the UE may take the N_(TA) ^(offset)into consideration when performing random access and transmitting otherUL data and control information, i.e., the starting timing of ULsubframes sent by the UE is (N_(TA)+N_(TA) ^(offset))×T_(S) secondsprior to the starting timing of DL subframes received by the UE from thecell. The N_(TA)×T_(S) denotes the TA configured for the UE when thecell conforms to LTE Release 11. During random access, N_(TA)=0, and theUE determines the TA of the random access preamble signal is N_(TA)^(offset)×T_(S) based on the configured parameter N_(TA) ^(offset). Assuch, the cell coverage supported by the PRACH preamble signal can bemaintained unchanged, and transmission performances of other UL data andcontrol information are also guaranteed.

When the UE works only in one cell that has configured with N_(TA)^(offset), if the N_(TA) ^(offset) is configured for the cell via RRCsignaling in block 402, the UE only takes the N_(TA) ^(offset) intoconsideration during transmission of UL data and control informationafter the UE has accessed the cell in the system, i.e., starting timingof UL subframes sent by the UE is (N_(TA)+N_(TA) ^(offset))×T_(S)seconds prior to starting timing of DL subframes received by the UE fromthe cell. This guarantees transmission performances of UL data andcontrol information.

EXAMPLE TWO

In a CA system where CA is applied to both FDD cells and TDD cells,timing of a base station receiving UL subframes in a cell may beadjusted to make starting timing of UL subframes of a UE in FDD cellsand TDD cells become consistent with or close to each other. Suppose aUE has accessed a cell in the CA system, and the cell is a Pcell. Whenthe UE needs to be configured to work in another cell, e.g., an Scell,starting timing of an UL subframe of the UE also needs to be adjusted toguarantee system performances.

There are three situations.

In the first possible situation, suppose the Scell newly added belongsto a TA group (TAG) to which the Pcell belongs, UL transmission in theScell uses the same TA with that used in the Pcell. The Scell may be anFDD cell or a TDD cell. N_(TA)×T_(S) denotes the TA configured for theUE when the Pcell conforms to LTE Release 11.

Supposing the Pcell is an FDD cell and starting timing of a UL subframeof the UE in the Pcell is (N_(TA)+N_(TA offset))×T_(S) seconds (e.g.N_(TA offset)=0) prior to, starting timing of a DL subframe received bythe UE in the Pcell according a timing mechanism specified in LTERelease 11, starting timing of a UL subframe of the UE in the newlyadded Scell is (N_(TA)+N_(TA offset))×T_(S)=N_(TA)×T_(S) seconds priorto starting timing of the DL subframe received by the UE from the Pcell.

In another example, supposing the Pcell is an FDD cell and startingtiming of a UL subframe of the UE in the Pcell is(N_(TA)+N_(TA offset))×T_(S) seconds (e.g., N_(TA offset)×T_(S)=20 us)prior to starting timing of a DL subframe received by the UE in thePcell, starting timing of a UL subframe of the UE in the Scell is(N_(TA)+N_(TA offset))×T_(S) seconds prior to starting timing of the DLsubframe received by the UE from the Pcell. N_(TA offset)×T_(S) denotesthe TA to be added to the Pcell obtained by using the first manner ofhandling TA in block 402. In an example, the base station may configureda TA for the UE which has already included the extra N_(TA offset)×T_(S)seconds, i.e., the base station may configure the TA of the UE to be(N_(TA)+N_(TA offset))×T_(S) seconds. In another example, the basestation conforms to LTE Release 11 and configures the TA of the UE to beN_(TA)×T_(S) seconds, and the UE adds N_(TA offset)×T_(S) seconds to theTA during UL transmission, i.e., the actual TA is(N_(TA)+N_(TA offset))×T_(S) seconds.

In yet another example, supposing the Pcell is an FDD cell and startingtiming of a UL subframe of the UE in the Pcell is determined by using atiming offset parameter N_(TA) ^(offset) which is sent through broadcastsignaling or via RRC signaling, i.e., starting timing of the UL subframeof the UE is (N_(TA)+N_(TA) ^(offset))×T_(S) seconds prior to thestarting timing of a DL subframe received by the UE from the Pcell,starting timing of the UE in the Scell may be (N_(TA)+N_(TA)^(offset))×T_(S) seconds prior to the starting timing of the DL subframereceived by the UE from the Pcell. The N_(TA) ^(offset)×T_(S) denotesthe TA to be added to the Pcell obtained by using the second manner ofhandling TA in block 402. In an example, the base station may configureda TA for the UE which has already included the extra N_(TA)^(offset)×T_(S) seconds, i.e., the base station may configure the TA ofthe UE to be (N_(TA)+N_(TA) ^(offset))×T_(S) seconds. In anotherexample, the base station conforms to LTE Release 11 and configures theTA of the UE to be N_(TA)×T_(S) seconds, and the UE adds N_(TA)^(offset)×T_(S) seconds to the TA during UL transmission, i.e., theactual TA is (N_(TA)+N_(TA) ^(offset))×T_(S) seconds.

Supposing the Pcell is a TDD cell and starting timing of a UL subframeof the UE in the Pcell is (N_(TA)+N_(TA offset))×T_(S) seconds (e.g.,N_(TA offset)=624) prior to starting timing of a DL subframe received bythe UE from the Pcell according a timing mechanism specified in LTERelease 11, starting timing of a UL subframe of the UE in the Scell maybe (N_(TA)+N_(TA offset))×T_(S) seconds prior to the starting timing ofthe DL subframe received by the UE from the Pcell. The N_(TA offset)^(T) _(S) denotes the TA to be added to the Pcell obtained by using thefirst manner of handling TA in block 402. In an example, the basestation may configured a TA for the UE which has already included theextra N_(TA offset)×T_(S) seconds, i.e., the base station may configurethe TA of the UE to be (N_(TA)+N_(TA offset))×T_(S) seconds. In anotherexample, the base station conforms to LTE Release 11 and configures theTA of the UE to be N_(TA)×T_(S) seconds, and the UE addsN_(TA offset)×T_(S) seconds to the TA during UL transmission, i.e., theactual TA is (N_(TA)+N_(TA offset))×T_(S) seconds.

In still another example, supposing the Pcell is a TDD cell and startingtiming of a UL subframe of the UE in the Pcell is determined by using atiming offset parameter N_(TA) ^(offset) which is sent through broadcastsignaling or via RRC signaling, i.e., starting timing of the UL subframeof the UE is (N_(TA)+N_(TA) ^(offset))×T_(S) seconds prior to thestarting timing of a DL subframe received by the UE from the Pcell,starting timing of the UE in the Scell may be (N_(TA)+N_(TA)^(offset))×T_(S) seconds prior to the starting timing of the DL subframereceived by the UE from the Pcell. The N_(TA) ^(offset)×T_(S) denotesthe TA to be added to the Pcell obtained by using the second manner ofhandling TA in block 402. In an example, the base station may configureda TA for the UE which has already included the extra N_(TA)^(offset)×T_(S) seconds, i.e., the base station may configure the TA ofthe UE to be (N_(TA)+N_(TA) ^(offset))×T_(S) seconds. In anotherexample, the base station conforms to LTE Release 11 and configures theTA of the UE to be N_(TA)×T_(S) seconds, and the UE adds N_(TA)^(offset)×T_(S) seconds to the TA during UL transmission, i.e., theactual TA is (N_(TA)+N_(TA) ^(offset))×T_(S) seconds.

In the second possible situation, supposing the newly added Scell doesnot belong to the TAG to which the Pcell belongs, the Scell may be anFDD cell or a TDD cell, and a TAG to which the Scell belongs has alreadyinclude at least one another Scell, starting timing of a UL subframe inthe Scell may be determined according to starting timing of UL subframesin a second Scell which is used for determining UL timing in the TAG towhich the Scell belongs. The process is similar to the above method fordetermining starting timing of UL subframes according to the Pcell withthe Pcell in the above method replaced with the second Scell fordetermining UL timing in the TAG. The N_(TA)×T_(S) denotes the TAconfigured for the UE when the second Scell for determining UL timingconforms to LTE Release 11, the N_(TA offset)×T_(S) denotes the extra TAadded to the second Scell, and the N_(TA) ^(offset) denotes controlinformation for starting timing of UL subframes sent by the secondScell.

In the third possible situation, supposing the newly added Scell doesnot belong to the TAG to which the Pcell belongs and the Scell is thefirst Scell (: first and only member) in a TAG to which the Scellbelongs, the base station needs to trigger the UE to perform randomaccess in the Scell to obtain TA needed by the UE, and thus control ULtransmission of the UE in the Scell. The Scell may be an FDD cell or aTDD cell. N_(TA)×T_(S) denotes the TA configured for the UE when thenewly added Scell conforms to LTE Release 11.

In this third situation, one of possible manners is to make startingtiming of a UL subframe of the UE (N_(TA)+N_(TA offset))×T_(S) seconds(e.g. N_(TA offset)=624) prior to starting timing of a DL subframereceived by the UE from the Scell in block 402. The N_(TA offset)×T_(S)denotes the TA to be added to the Scell obtained by using the firstmanner of handling TA in block 402. In an example, the base station mayconfigured a TA for the UE which has already included the extraN_(TA offset)×T_(S) seconds, i.e., the base station may configure the TAof the UE to be (N_(TA)+N_(TA offset))×T_(S) seconds. In anotherexample, the base station conforms to LTE Release 11 and configures theTA of the UE to be N_(TA)×T_(S) seconds, and the UE addsN_(TA offset)×T_(S) seconds to the TA during UL transmission, i.e, theactual TA is (N_(TA)+N_(TA offset))×T_(S) seconds. In an example, the UEmay use N_(TA offset)=624 during an initial random access process, i.e.,compared to the mechanism where it is pre-defined that N_(TA)=0, thestarting timing for sending the PRACH preamble signal may be determinedto be N_(TA offset)×T_(S)=20 us prior to the starting timing of a DLsubframe received by the UE from the Scell. As such, the cell coverageof the PRACH preamble signal can be maintained unchanged.

Another possible manner may include configuring a timing offsetparameter N_(TA) ^(offset) for the Scell in block 401. The N_(TA)^(offset)×T_(S) denotes the TA to be added to the Scell obtained byusing the second manner of handling TA in block 402. The N_(TA)^(offset) may be sent in broadcast signaling of the Scell, or sent toeach UE via RRC signaling in the Scell. In an example, the N_(TA)^(offset) may be sent via RRC signaling sent by a Pcell for configuringthe Scell.

At block 402, if the N_(TA) ^(offset) is sent by the Pcell through RRCsignaling for configuring the Scell, the UE may take the N_(TA)^(offset) into consideration when performing random access andtransmitting other UL data and control information, i.e., startingtiming of a UL subframe of the UE is (N_(TA)+N_(TA) ^(offset))×T_(S)seconds prior to starting timing of a DL subframe received by the UEfrom the Scell. In an example, the base station may configured a TA forthe UE which has already included the extra N_(TA) ^(offset)×T_(S)seconds, i.e., the base station may configure the TA of the UE to be(N_(TA)+N_(TA) ^(offset))×T_(S) seconds. In another example, the basestation conforms to LTE Release 11 and configures the TA of the UE to beN_(TA)×T_(S) seconds, and the UE adds N_(TA) ^(offset)×T_(S) seconds tothe TA during UL transmission, i.e., the actual TA is (N_(TA)+N_(TA)^(offset))×T_(S) seconds. During random access, N_(TA)=0, and the UEdetermines the TA of the random access preamble signal is N_(TA)^(offset)×T_(S) based on the configured parameter N_(TA) ^(offset). Assuch, the cell coverage supported by the PRACH preamble signal can bemaintained unchanged, and transmission performances of other UL data andcontrol information are also guaranteed.

In another example, at block 402, if the N_(TA) ^(offset) is sent in theScell through broadcast signaling, the UE may take the N_(TA) ^(offset)into consideration when performing random access and transmitting otherUL data and control information, i.e., starting timing of a UL subframeof the UE is (N_(TA)+N_(TA) ^(offset))×T_(S) seconds prior to startingtiming of a DL subframe received by the UE from the Scell. In anexample, the base station may configured a TA for the UE which hasalready included the extra N_(TA) ^(offset)×T_(S) seconds, i.e., thebase station may configure the TA of the UE to be (N_(TA)+N_(TA)^(offset))×T_(S) seconds. In another example, the base station conformsto LTE Release 11 and configures the TA of the UE to be N_(TA)×T_(S)seconds, and the UE adds N_(TA) ^(offset)×T_(S) seconds to the TA duringUL transmission, i.e., the actual TA is (N_(TA)+N_(TA) ^(offset))×T_(S)seconds. During random access, N_(TA)=0, and the UE determines the TA ofthe random access preamble signal is N_(TA) ^(offset)×T_(S) based on theconfigured parameter N_(TA) ^(offset). As such, the cell coveragesupported by the PRACH preamble signal can be maintained unchanged, andtransmission performances of other UL data and control information arealso guaranteed.

In another example, at block 402, if the N_(TA) ^(offset) is sent in theScell through RRC signaling, the UE may take the N_(TA) ^(offset) intoconsideration when transmitting other UL data and control informationafter the UE has accessed the Scell in the system, i.e., starting timingof a UL subframe of the UE is (N_(TA)+N_(TA) ^(offset))×T_(S) secondsprior to starting timing of a DL subframe received by the UE from theScell. This guarantees transmission performances of UL data and controlinformation. In an example, the base station may configured a TA for theUE which has already included the extra N_(TA) ^(offset)×T_(S) seconds,i.e., the base station may configure the TA of the UE to be(N_(TA)+N_(TA) ^(offset))×T_(S) seconds. In another example, the basestation conforms to LTE Release 11 and configures the TA of the UE to beN_(TA)×T_(S) seconds, and the UE adds N_(TA) ^(offset)×T_(S) seconds tothe TA during UL transmission, i.e., the actual TA is (N_(TA)+N_(TA)^(offset))×T_(S) seconds.

Corresponding to the above method, examples of the present disclosurealso provide an apparatus.

FIG. 5 is a schematic diagram illustrating modules of the apparatus inaccordance with an example of the present disclosure.

An apparatus (500) includes a transceiver (520) that transmits andreceives various signals and a controller (510) that controlstransmission and reception of a control channel and a communicationsignal through the transceiver (520). The controller (510) generallycontrols operations of the method described in FIG. 4 as well as thecontrol of the transceiver 520. Accordingly, performance of anyoperation by the apparatus can be equally understood as performance ofany operation by the controller (510) of the apparatus in thespecification.

Although the transceiver (520) and the controller (510) may beimplemented by separated modules, such as a Radio Frequency (RF) moduleand a processor, it should be noted that they can be implemented by asingle module.

The controller (510) may include a configuring module (501) and anadjusting module (503).

The configuring module (501) is configured to receive configurationinformation, and performing carrier aggregation (CA) of frequencydivision duplex (FDD) cells and time division duplex (TDD) cells byusing the configuration information; and the adjusting module (503) isconfigured to adjust starting timing of a UL subframe in a cellparticipating in the CA.

The controller (510) may include a processor and a memory, and thememory may store the communication signal transmitting/receivingoperation in a form of instructions which can be read and executed bythe processor.

The components of the apparatus, modules and the like used in thedisclosure may operate by using a hardware circuit, for example, acombination of a complementary metal oxide semiconductor based logicalcircuit, firmware, software and/or hardware, and a combination offirmware and/or software inserted into a machine-readable medium. As anexample, various electric configurations and methods may be carried outby using electric circuits such as transistors, logic gates, and anApplication Specific Integrated Circuit (ASIC).

What is claimed is:
 1. A method of configuring timing of an uplink (UL)transmission of a carrier aggregation (CA) system, the methodcomprising: obtaining, by a user equipment (UE), a timing advance offsetfor the CA system for a first cell and a second cell; receiving, by theUE, a timing advance between a downlink and an uplink, wherein thetiming advance is configured by a base station (BS) for the first cell;adjusting, by the UE, an uplink timing of a UL transmission in thesecond cell based on the timing advance offset and the timing advance;and transmitting an uplink signal in the second cell based on theadjusted uplink timing, wherein the first cell and the second cellbelong to a same time advance group (TAG), wherein the timing advanceoffset is same for the first cell and the second cell, and wherein thetime advance offset is applied for a random access process in the firstcell.
 2. The method of claim 1, wherein adjusting, by the UE, the uplinktiming of the UL transmission in the second cell comprises: making astarting timing of the UL transmission in the second cell (the timingadvance+the timing advance offset)*(a timing unit) seconds prior to astarting timing of a downlink (DL) transmission.
 3. The method of claim1, wherein the timing advance offset is obtained from a radio resourcecontrol (RRC) signal.
 4. The method of claim 1, wherein an uplink timingof an UL transmission in the first cell is adjusted by using the timingadvance offset and the timing advance.
 5. The method of claim 1, whereinthe timing advance offset is pre-defined.
 6. An apparatus forconfiguring timing of an uplink (UL) transmission of a carrieraggregation (CA) system, the apparatus comprising: a transceiver coupledto at least one processor; a memory coupled to the at least oneprocessor; and the at least one processor configured to: obtain a timingadvance offset for the CA system for a first cell and a second cell,receive a timing advance between a downlink and an uplink, wherein thetiming advance is configured by a base station (BS) for the first cell,adjust an uplink timing of a UL transmission in the second cell based onthe timing advance offset and the timing advance, and transmit an uplinksignal in the second cell based on the adjusted uplink timing, whereinthe first cell and the second cell belong to a same time advance group(TAG), wherein the timing advance offset is same for the first cell andthe second cell, and wherein the time advance offset is applied for arandom access process in the first cell.
 7. The apparatus of claim 6,wherein the at least one processor is configured to make a startingtiming of the UL transmission in the second cell (the timing advance+thetiming advance offset)*(a timing unit) seconds prior to a startingtiming of a downlink (DL) transmission.
 8. The apparatus of claim 6,wherein the timing advance offset is obtained from a radio resourcecontrol (RRC) signal.
 9. The apparatus of claim 6, wherein an uplinktiming of an UL transmission in the first cell is adjusted by using thetiming advance offset and the timing advance.
 10. The apparatus of claim6, wherein the timing advance offset is pre-defined.